1. Field of the Invention
The present invention is generally directed to processing modulated wired infra-red (“WIR”) signals. More particularly, the present invention is directed to the demodulation of a modulated WIR signal. The invention is particularly useful in media management products such as televisions, video cassette recorders, stereos, DVD players, DVD and Music Managers, and other like devices. However, the invention is equally applicable to demodulating WIR signals in other scenarios as well.
2. Description of Related Art
Known media management products include a capability of being controlled externally by Wired Infrared (“WIR”) signals. For example, one such media management device is the Fireball® DVD and Music Manager DVDM-100 offered and sold by Escient of Indianapolis, Ind. Such media management products usually require circuitry that receives and processes WIR signals since such signals are commonly generated by a variety of home control and/or automation systems. WIR signals may also be generated by off the shelf Infrared (“IR”) repeater modules. This capability allows certain known devices to interface to such external control devices for the purposes of being integrated into a customer's existing installation. Integration provides a means of controlling such media management devices from existing premise's home automation control devices.
FIG. 1 illustrates a typical arrangement of a WIR control input subsystem 10. In this arrangement, subsystem 10 comprises essentially two processing elements. These two elements are operatively coupled to one another while receiving a modulated WIR input signal 12 and producing a baseband IR signal 16. This baseband IR signal 16 is then provided to an IR command decoder 18. IR command decoder 18 decodes signal 16 into an actual command 20 for operation of media management products such as televisions, video cassette recorders, stereos, DVD players, DVD and Music Managers, and other like devices.
In the architecture 10 illustrated in FIG. 1, the first processing element comprises an input signal demodulator and the second processing element comprises an IR command decoder. The first processing element, WIR demodulator 14, receives the modulated WIR input signal 12. WIR demodulator 14 typically strips the modulated WIR input signal of its carrier frequency. WIR demodulator 14 then provides a baseband demodulated IR signal 16 to an IR command decoder 18.
Baseband IR signal 16 is analyzed by IR command decoder 18. IR command decoder 18 decodes the baseband IR signal into a number of supported IR control commands. Such commands could include, but may not be limited to, such commands as Stop, Play, Eject, Rewind, Fast Forward, Skip, etc. This second processing element is typically implemented using a programmed microcontroller. The IR command decoder 18 then outputs a decoded IR command 20.
FIG. 2A illustrates one arrangement 30 of a typical WIR modulated input signal, such as the WIR modulated input signal 12 illustrated in FIG. 1. Such a modulated input signal ordinarily comprises a carrier pulse burst comprising a plurality of pulses. For example, in FIG. 2A, WIR modulated input signal 12 comprises two pulse bursts 31, 32. However, those of ordinary skill in the relevant art will recognize that other modulated signal pulse arrangements may be used as well. In a typical arrangement, the modulated signal 30 will include a carrier frequency on the order of approximately 35 to 70 kHz. Other carrier frequencies may also be used.
FIG. 2B illustrates one arrangement 33 of an inverted WIR modulated input signal, such as the WIR modulated input signal 30 illustrated in FIG. 2A. As illustrated in FIG. 2A, the modulated input signal 33 comprises two inverted pulse bursts. In certain applications, the WIR modulated input signal may not be inverted before a WIR baseband output signal is generated. FIG. 2C illustrates one arrangement 36 of a typical WIR Baseband Output Signal, such as the WIR Baseband Output Signal 16 illustrated in FIG. 1. The WIR baseband output signal 36 is derived from WIR modulated input signal 30 of FIG. 2A or, alternatively, derived from WIR modulated input signal 33 of FIG. 2B.
Certain known media management products have implemented the above mentioned WIR demodulation device of the WIR input subsystem by using generally known infrared electronics components, primarily analog based infrared electronics components. One such typical implementation of a WIR demodulation apparatus 40 is illustrated in FIG. 3. As illustrated in FIG. 3, this known WIR demodulation apparatus 40 receives a modulated WIR input signal 46 and generates a baseband WIR signal 44 based on this input signal 46. WIR demodulation apparatus 40 comprises an IR transmitter 48 and an IR receiver/demodulator 52. IR transmitter 48 receives modulated WIR input signal 46, such as input signal 30 illustrated in FIG. 2A. IR transmitter 48 transmits an optical signal 68 across an air gap 50. Optical signal 68 is received by IR receiver/demodulator 52.
In this typical arrangement, IR receiver/demodulator 52 comprises various analog based electrical components. Such components include an input stage or an IR receiving device 54, an adjustable gain controller (“AGC”) 56, a band pass filter 58, a demodulator 60, and a controller 62. Controller 62, which receives an input signal from band pass filter 58, provides an input to both AGC 56 as well as demodulator 60.
IR transmitter 48 converts modulated WIR input signal 46 to an emitted optical signal 68, preferably using an LED. Emitted optical signal 68 must then be aimed at IR receiver 54 which is part of IR receiver/demodulator 52. The IR receiver/demodulator is typically available as an off the shelf electronic component such as a Vishay part number TSOP1130, and various others. IR receiver/demodulator 52 generates baseband WIR signal 44 which is then provided to the IR command decoder 66.
Although the demodulator 40 has certain advantages, there are a number of disadvantages to using IR transmitter 48 along with the IR receiver/demodulator apparatus 52 illustrated in FIG. 3. For example, because modulated WIR input signal 46 must be converted to an optical signal 68, the apparatus requires an air gap 50. This air gap requirement adds additional requirements in calibrating the width of the air gap 50 as well as the power level of the transmitted optical signal 68 in order to ensure a proper optical detection at the input stage 54 and subsequent generation of baseband WIR signal 44.
Aside from the difficulty of maintaining adequate clearance between the IR transmitter and the input stage 54, providing this air gap results in a greater demand for surface area, especially surface area along a printed circuit board resulting in certain space limitations. Moreover, the typical IR receiver/demodulator 52 used in apparatus 40 is usually calibrated for proper operation around a fixed IR carrier frequency, Fc. This requires the actual carrier frequency F in WIR transmitted signal 68 to be centered around Fc within a typical given operating tolerance of ±5% (i.e. F=Fc±5%). This operating tolerance tends to provide a proper detection and demodulation of IR signal 68 resulting in a valid baseband WIR signal 44. Consequently, the apparatus 40 in FIG. 3 is not programmable so as to operate at a plurality of different carrier frequencies.
Therefore, a need exists for an improved system that does not require printed circuit board surface area to be used for an air gap. There is also a general need for an apparatus that does not rely on analog based devices, such as an analog demodulator. There is also a general need for an apparatus that is programmable, for example, a programmable demodulator that can efficiently and cost effectively demodulate more than one carrier frequency without costly hardware changeovers. Preferably, such a programmable demodulator may be field programmable and even more preferably, such a programmable demodulator may be programmable over the Internet and/or a phone line.